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author | Tim Bird <tim.bird@am.sony.com> | 2012-02-08 10:37:57 -0800 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-08 16:51:45 -0800 |
commit | 3bcfa431334d99fa8bff96c4e7c2108f0b26242e (patch) | |
tree | d94aa3adb216c2027e17a95f0556a06d427877d5 | |
parent | c626224de9370ae783e8b0cb6aaca2ba3d81fe62 (diff) | |
download | op-kernel-dev-3bcfa431334d99fa8bff96c4e7c2108f0b26242e.zip op-kernel-dev-3bcfa431334d99fa8bff96c4e7c2108f0b26242e.tar.gz |
staging: android: logger: simplify and optimize get_entry_len
Make this code slightly easier to read, and eliminate calls
to sub-routines. Some of these were previously optimized away
by the compiler, but one memcpy was not.
In my testing, this makes the code about 20% smaller, and
has no sub-routine calls and no branches (on ARM).
v2 of this patch is, IMHO, easier to read than v1. Compared to
that patch it uses __u8 instead of unsigned char, for
consistency with the __u16 val data type, simplifies the
conditional expression, adds a another comment, and
moves a common statement out of the if.
Signed-off-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | drivers/staging/android/logger.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c index 29ee137..1e9e638 100644 --- a/drivers/staging/android/logger.c +++ b/drivers/staging/android/logger.c @@ -93,20 +93,24 @@ static inline struct logger_log *file_get_log(struct file *file) * get_entry_len - Grabs the length of the payload of the next entry starting * from 'off'. * + * An entry length is 2 bytes (16 bits) in host endian order. + * In the log, the length does not include the size of the log entry structure. + * This function returns the size including the log entry structure. + * * Caller needs to hold log->mutex. */ static __u32 get_entry_len(struct logger_log *log, size_t off) { __u16 val; - switch (log->size - off) { - case 1: - memcpy(&val, log->buffer + off, 1); - memcpy(((char *) &val) + 1, log->buffer, 1); - break; - default: - memcpy(&val, log->buffer + off, 2); - } + /* copy 2 bytes from buffer, in memcpy order, */ + /* handling possible wrap at end of buffer */ + + ((__u8 *)&val)[0] = log->buffer[off]; + if (likely(off+1 < log->size)) + ((__u8 *)&val)[1] = log->buffer[off+1]; + else + ((__u8 *)&val)[1] = log->buffer[0]; return sizeof(struct logger_entry) + val; } |